1. Field of the Invention
The present invention relates generally to jet fan devices and more specifically it relates to a vectorized jet fan device for providing a jet fan which is capable of being utilized as a ventilation fan device for turning the flow of airstream from the fan by a small angle and increasing the airstream velocity through a smaller diameter silencer for efficiently meeting and utilizing space clearance and improving aerodynamic and ventilation performance.
2. Description of the Related Art
Jet fan devices have been in use for years. Typically, conventional jet fan devices are tubular in shape. Such a jet fan device generally consists of a fan-motor unit, for which the nominal diameter and typical length of the fan housing is represented by “D”, and on each end of the fan housing, there is a tubular “silencer” that is used to reduce the aerodynamic noise from the high speed air flow from the fan. The length of the silencer generally varies and is typically 2D. The interior diameter of the silencers and fan housing are generally the same and through which air is drawn in from one end and discharged towards the other end. The “silencer-fan-silencer” jet fan device therefore forms a straight-through flow device, which is typically installed using a jet fan support system including hang from the ceiling, attach to the sidewalls or the ground. This device is generally used for space ventilation and control of fire and smoke, particularly for vehicular tunnels.
While conventional jet fan devices may be suitable for the particular purpose to which they address, the main problems of using these devices are installation space clearance and aerodynamic performance. As most often there is limited space for installation of these devices, which limits the diameter of the fan that can be used. And usually the jet fan devices are installed close to the wall, where for the high speed flow of the air stream discharged from the device, the flow speed may be as high as 6,000 to 8,000 feet per minute. The proximity of this air stream to the wall generally causes extra friction losses at the wall, which then may significantly reduce the aerodynamic performance.
One approach to address these problems for conventional jet fan devices is a special design configuration of a niche at the structural wall, where the surface of the wall for jet fan installation has to be recessed by a certain distance, so as to satisfy installation space clearance. The transition from the recessed surface is typically an inclined surface of a small degree of angle, generally extending for an extended distance from either end of the jet fan device. The cost of labor for constructing and maintaining the niche space such as for cleaning of debris can be very expensive.
To our knowledge there are no examples of US patents on jet fan devices that fully address both problems of installation space clearance and aerodynamic performance. The only illustrative example of prior art is German Patent No. 1050684 to Witt, which discloses a jet fan device with a customized slanted silencer attached to the fan. The silencer and so its airway is inclined at a small angle, typically 7 degrees from the fan housing centerline, so that the discharged air stream is directed away from the wall surfaces, which has shown convincing proofs of advantageous aerodynamic performance from a number of field testing in vehicular tunnels (4). It was claimed that 25-50% reduction in losses could be achieved as opposed to using conventional jet fan devices. Due to the slanted silencer design, the installation space of such devices, however, is generally larger than conventional jet fan devices.
In these respects, the vectorized jet fan according to the present invention substantially departs from the conventional devices and designs of the prior art, and in so doing provides a device primarily developed for the purposes of efficiently meeting and utilizing space clearance, and improving aerodynamic performance.